Multiple Indexers in C#

In C#, you can’t have multiple indexers like you can do in VB, so the following code is not supported:

class C
{
public Foo Foos[int i]
{

}
public Bar Bars[int i]
{

}
}

On the other hand, exposing internal IEnumerable is not always a desired solution (because you want to limit access to your internal collections – that’s why indexers are for in the first place.)

Workaround

I came up with this simple class that you can add to your code:

public class IndexProperty<T,I>
{
private Func<I,T> getter;
private Action<I, T> setter;

public IndexProperty(Func<I, T> g, Action<I, T> s)
{
if (g == null || s == null)
throw new ArgumentNullException();
getter = g;
setter = s;
}

public T this[I index]
{
get
{
return getter(index);
}
set
{
setter(index, value);
}
}
}

Now, you can add multiple indexers to your class, but make sure you initialize the indexers properly. The following example demonstrates how to expose multiple indexers:

public class MyClass
{
private List<string> myList = new List<string>();
public MyClass()
{
myList.AddRange(new string[]{“1″,”2″,”3”});
// Init the IndexProperty with your methods (or lambdas)
this.Keys=new IndexProperty<string,int>(
i=> myList[i],
(j,val)=> myList[j]=val);
}

public IndexProperty<string,int> Keys { get; set; }
}

The following code demonstrates how your class can be used:

static void SampleMethod()
{
MyClass c = new MyClass();
c.Keys[0] = “value”;
}

Ref: http://www.codeproject.com/Tips/319825/Multiple-Indexers-in-Csharp

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Posted on January 18, 2013, in Uncategorized. Bookmark the permalink. Leave a comment.

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